Typically, a rotor blade for wind turbines comprises a spar for transferring the load from the rotor blade to the hub. Different kinds of forces act on the blade in use. A first is the centrifugal force acting on the blade in a longitudinal direction of the blade. This force is caused by the rotation of the blade about the hub. A second kind is forces acting on the rotor blade in a thickness direction i.e. a direction extending through the leeward and the windward side of the rotor blade. These forces are caused by the wind acting on the blade. A third kind is forces acting on the rotor blade in a chord direction i.e. a direction extending through the leading edge and the trailing edge of the rotor blade. These forces are caused by gravity, when the blade extends in the horizontal direction or in any other direction transverse to the vertical direction.
As the size of wind turbines increases, the rotor blades have increasing length, thickness and width. The centre of elasticity of the blade is highly dependent on the position of the spar inside the blade. Thus with increased width of the blade, the distance from the trailing edge and/or the leading edge to centre of elasticity is increased. This causes the blade to be more vulnerable to the third kind of abovementioned forces, i.e. forces in the chord direction, as the edgewise stiffness decreases.
It is an object of embodiments of the present invention to provide a rotor blade which has an improved ability of transferring load in the direction of the chord.